1. Field of the Invention
This invention relates to a method for heat treatment such as annealing or the like of metal strips which comprises allowing a metal strip to pass through a heating zone and a cooling zone.
2. Description of the Prior Art
The usual method of heat treating metal strips (namely, long belt-shaped plates of aluminum, copper, iron, or the like obtained by continuous rolling using a rolling mill and normally having thicknesses of 3.5 mm or less and a variety of widths) is by allowing them to pass through a heating zone and a cooling zone in a floating manner. In this process, however, when the buckling stress resistance of the metal strip is weaker than the thermal stress produced in the strip in the transverse direction thereof, parallel wrinkles (FIG. 11) are formed in the strip in the travelling direction thereof, leading to the production of a defective treated product.